HOME ORCHARD HOME ORCHARD DISEASE AND PEST MANAGEMENT GUIDE PREFACE Elizabeth Little, Extension Plant Pathologist Brett Blaauw, John All and Dean Kemp, Entomologists Home orchard disease and pest management guides suggest cultural and chemical control practices that offer a reasonable degree of protection from pests. Home orchardists should be aware that producing commercial quality, blemish-free fruit in Georgia’s climate is difficult. During the growing season, the crop should be monitored at least weekly for any emerging pest problems. Fungicides and insecticides work best when pest levels are low. Recommendations attempt to time applications just before and through typical peaks in pest abundance. Fine tuning the time of application to what you see in your orchard will help minimize pest damage. To be effective, fungicides need to be applied before appearance of symptoms and/or just prior to and during weather conditions favorable for disease development. Many fruit diseases are favored by cool-to-mild periods with moderate-to-high amounts of rainfall and humidity. Pruning and removal of diseased and/or dead twigs and branches, raking and removal of leaves and debris, regular mowing around vines, trees or bushes, and disposing of rotten and/or diseased fruit, improves disease and insect control. Collectively these practices are referred to as sanitation. Sanitation, in combination with choosing disease-resistant cultivars and the as-needed use of chemicals, will optimize control. Pest pressure in home orchards is often as high, or higher, than is experienced in commercial orchards. Edge effect – higher pest abundance where two different habitat types meet – is common in commercial orchards. In home orchards, all of the trees, bushes, or vines fall within the “border rows,” so pest pressure is frequently high. Home garden pesticide labels, which should be retained on all pesticide containers, indicate on what crops that particular product may be used. Federal law clearly restricts the use of any pesticides to the crops or sites, listed on the package’s label. Home garden pesticides for use on fruits must specifically list fruits, or cite individual fruits, such as apples, pears, or peaches. Pesticide labels are based on rigorous food, applicator, and environmental safety considerations, and they are legally binding. Always read the pesticide label before application. Pesticide options for managing home orchard pests are modest. While many different trade-named products are available, there are relatively few active ingredients. The effectiveness of, and the range of pests controlled by, any product is determined by its active ingredient(s) and rate. Dose, the amount of product applied, is determined by two factors: the amount applied (tablespoons, fluid ounces, or ounces) and by the active ingredient’s concentration. The amount of product applied is limited by the product label. Higher label dosages normally provide better control. Remember, by following the product label you are assured of using safe amounts. Sometimes products containing the same active ingredients will have varying amounts of active ingredient. General considerations for home orchard pesticide applicators include: • Wear goggles or other eye protection to shield yourself from spray drift; • Wear long sleeves, long trousers, a hat, and shoes; • Remove and launder clothing worn while applying pesticides; launder these clothes separately from family laundry before reusing them; • Always check for and follow the pre-harvest interval(s) listed on the pesticide container(s). If you are mixing more than one product, follow the longest listed pre-harvest interval; • Many insecticides, and some fungicides, are toxic to honey bees as well as other pollinators. Do not spray during bloom unless the product label specifically recommends bloom sprays, and do not apply insecticides if bees are foraging on orchard weeds; • Assume pesticides to be toxic to fish and other non-target organisms, do not apply to water or where runoff can occur; • Keep pets and children away from treated areas. Consider alternatives to toxic pesticides when treating close to residences or if there is a risk for non-target exposure; • Store pesticides securely and only in the original container. UGA Extension Special Bulletin 48 • Georgia Pest Management Handbook – 2020 Home & Garden Edition 37 HOME APPLE AND PEAR (POME FRUIT) DISEASE AND INSECT GUIDE Elizabeth Little, Extension Plant Pathologist Brett Blaauw, Extension Entomologist APPLE AND PEAR DISEASES Successful production of apples in Georgia is difficult and requires careful management. Diseases are threats not only to the apple fruit, but also to tree health. The most important disease threats are fire blight and the summer rots (black, white, and bitter rots). Secondary diseases that will sometimes be important include the leaf spots, powdery mildew, and, in the mountains and upper piedmont, scab. All of these diseases can be at least partially controlled by using preventative measures, starting with selecting the appropriate apple cultivars, and choosing a good site. Apple trees must be properly pruned, especially when young, to develop a strong open structure, and careful attention must be paid to fertilization. Dead wood should be pruned out as soon as seen or immediately after leaf fall. Annual dormant pruning or tree training should not begin until trees are fully dormant (mid-January in north Georgia). Rake and, either, physically remove or thoroughly grind fallen leaves and mummified fruit with a mulching mower after leaf fall. Conscientious removal of diseased fruit and wood is important in reducing disease pressure. Many popular cultivars of European pears are next to impossible to grow in Georgia due to fire blight (see cultivar list at end of this section), but if appropriate cultivars are chosen, pears can be much easier to grow than apples. Besides fire blight, there are only a few minor pear diseases that may or may not need management. Fire blight, caused by the bacterium Erwinia amylovora, is a native disease that is a major problem on imported fruits (apples and pears). The bacterium survives in the previous year’s infected wood and enters the plant through the flowers. The antibiotic streptomycin is often used to prevent flower infections in susceptible cultivars in orchards with a history of fire blight, especially when the weather is wet and warm. Antibiotics need to be applied before rain and frequently as flowers open. Coppers also have some effect on bacteria, but are generally not used during bloom due to the potential for damage to the foliage and flowers. The bacterium moves from the infected flowers into the branches and can kill susceptible cultivars, especially young trees, in one season, in some cases even with antibiotic treatment. Therefore, choosing disease resistant cultivars of apples and pears is the most important management recommendation for home growers to prevent fire blight damage (see cultivar list at end of this section). Moderately resistant cultivars may not need any bloom sprays if the proper cultural practices are followed. When the weather conditions are optimal for infection during bloom (68-70º F with rain and humidity), the partially resistant cultivars suffer branch blight called “strikes,” but the disease will probably not kill the tree. Appropriate pruning, to open up the canopy and maintain tree health, and removal of diseased wood are important in preventing fire blight. Diseased wood should be removed by cutting 8-12 inches below the diseased tissue. Pruning tools can be dipped in disinfectant such as 10% bleach between cuts to prevent spread of the bacterium, especially when pruning is done when the disease is active in spring and early summer. The removed wood should be taken from the orchard and destroyed. Dormant copper sprays reduce winter survival of the pathogens. Excess vigor often increases susceptibility to fire blight and other diseases, so a balanced nutritional program is also important. There are many good publications available on growing healthy fruit trees. Black rot, bitter rot, and white rot are all caused by fungi that survive the winter on dead wood and old fruit in the tree and on the ground. Good sanitation practices are very important in reducing the impacts of these diseases. Dead branches, including fire blight “strikes” should be pruned out and destroyed. All old fruit should be removed from the tree and from the ground at the end of the season. Diseased fruit should be picked and destroyed as soon as they appear so the disease does not spread to other fruit on the tree. There are some cultivars of apple that have some resistance to the summer rots as well as fire blight (see list at end of this section). Fungicides may be needed and should be applied early in the season. Cedar-apple rust causes leaf spots on certain apple cultivars in some years if Eastern red cedar (Juniperus virginiana) trees are within approximately a quarter-mile. Removal of all cedar trees within that distance is generally impractical, so resistant cultivars are recommended (see cultivar list at end of this section). The fungus overwinters on the juniper, infecting the apple leaves during early leaf development. Fungicides can be sprayed during bloom if there has been a history of the disease causing significant defoliation of leaves. A similar rust goes to pear fruit (Cedar-quince rust), and hawthorn and mayhaw shoots and fruit (Cedar-hawthorn rust). Management is similar to cedar-apple rust. Sooty blotch and flyspeck may be the most common apple diseases in the Southeast, but the damage that they cause to the fruit is purely cosmetic and superficial. However, black, speckled, sooty looking fruit may not be pleasing to everyone. These diseases are more evident on yellow or green-fruited cultivars. Appropriate pruning for good air circulation in the canopy may be enough to manage these diseases. If needed, fungicides can be applied. Post-harvest washing of fruit in hot soapy water, followed by rinsing with clean water, will remove much of the sooty blotch and some flyspeck.